''De Furtivis Literarum Notis'' (''On the Secret Symbols of Letters'') is a 1563 book on

cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

written by

Giambattista della Porta Giambattista della Porta (; 1535 – 4 February 1615), also known as Giovanni Battista Della Porta, was an Italian scholar, polymath and playwright who lived in Naples at the time of the Renaissance, Scientific Revolution and Reformation. Giamba ...

. The book includes three sets of cypher discs for coding and decoding messages and a

substitution cipher In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, trip ...

improving on the work of

Al-Qalqashandi Shihāb al-Dīn Abū 'l-Abbās Aḥmad ibn ‘Alī ibn Aḥmad ‘Abd Allāh al-Fazārī al-Shāfiʿī better known by the epithet al-Qalqashandī ( ar, شهاب الدين أحمد بن علي بن أحمد القلقشندي; 1355 or 1356 &ndash ...

References

{{reflist 1563 books Cryptography books Non-fiction books